Heritability of cooperative behavior in the trust game

Abstract

Although laboratory experiments document cooperative behavior in humans, little is known about the extent to which individual differences in cooperativeness result from genetic and environmental variation. In this article, we report the results of two independently conceived and executed studies of monozygotic and dizygotic twins, one in Sweden and one in the United States. The results from these studies suggest that humans are endowed with genetic variation that influences the decision to invest, and to reciprocate investment, in the classic trust game. Based on these findings, we urge social scientists to take seriously the idea that differences in peer and parental socialization are not the only forces that influence variation in cooperative behavior.behavioral genetics ͉ cooperation ͉ experimental economics M any mutually beneficial transactions involve an element of interpersonal trust and may fail to materialize in the absence of an expectation that trust will be reciprocated. The prevalence of trust in a society has therefore been assigned primacy in a number of domains, for instance empirical (1) and theoretical (2) studies of economic growth. In recent years, the trust game (3) has emerged as a favorite instrument to elicit an individual's interpersonal trust and willingness to reciprocate trust. More generally, the game has been widely used to study cooperative behavior. In a trust game, an individual (the investor) decides how much money out of an initial endowment to send to another subject (the trustee). The sent amount is then multiplied by some factor, usually three, and the trustee decides how much of the money received to send back to the investor. The standard game-theoretic prediction for a single anonymous interaction between two purely self-interested individuals is for the investor to send nothing, rationally anticipating that the trustee will not reciprocate. Yet, experiments consistently show that cooperation flourishes in the trust game; the average investor sends a significant share of her endowment, and most trustees reciprocate (4). A voluminous body of theoretical and experimental work examines the mechanisms through which natural selection can favor cooperation, and proposed mechanisms include kin selection (5), reciprocity (6), indirect reciprocity (7), and group selection (8). These models offer different accounts for the ultimate explanation for the existence of cooperation and also generate different predictions about genotypic variation in equilibrium (9).To investigate whether humans are endowed with genetic variation that could help account for individual differences in trust game behavior, two separate teams of researchers independently conceived and executed a very similar experiment on twins [see supporting information (SI) for experimental procedures]. These teams became aware of each other for the first time after all data had been collected. One team recruited 658 subjects from the population-based Swedish Twin Registry, and the other team recruited 706 subjects from th...

On The Economics and Biology of Trust

“…The results of Reuter et al suggest that the distinction between social and asocial risk taking is indeed fundamental, as it even seems to be encoded in our genes. These results are also consistent with recent findings in a twin study (Cesarini et al 2008) that suggest that trust is partially heritable.…”

Trust and Volunteering: Selection or Causation? Evidence From a 4 Year Panel Study

“…Micro-level determinants of trust, however, have not yet been uncovered. Recent research in behavioral genetics reveals that trust measured by choices in a trust game (Cesarini et al 2008) as well as trust measured by verbal items similar to the items used in the present study (Hiraishi et al 2008) have only a small additive genetic component and is largely determined by nonshared environmental factors-characteristics of the environment unique to individuals. However, which characteristics of environments make people more or less trusting is unclear.…”

Genes, psychological traits and civic engagement

“…As a field, behaviour genetics represents an impressive collection of findings on the influence of genetic variation on a large range of behaviours, including: altruism [9], entrepreneurism [10], financial risk taking [9,11], impulsivity [12], intelligence [13,14], leadership [15][16][17], non-rational decision-making [18], smoking addiction [19], socioeconomic status [20] and trust [21]. Indeed, so widespread are findings of heritable behaviour that one scholar has coined the 'first law' of behaviour genetics: 'All human behavioural traits are heritable' [22].…”